The present invention relates to a process for preparing acetic acid esters by a vapor phase reaction, and more particularly to a process for the preparation of acetic acid esters by the reaction of acetic acid and aliphatic lower olefins, especially the preparation of ethyl acetate by the reaction of acetic acid and ethylene.
Processes for preparing carboxylic acid esters from olefins and carboxylic acids are carried out in the vapor phase or liquid phase. In the vapor phase reaction, an olefin gas is reacted with acetic acid vapor in the presence of a catalyst. The vapor phase reaction is advantageous in that the reaction is carried out under mild conditions without employing a reaction medium.
There are many reports on the catalysts used in the vapor phase reaction of olefins and carboxylic acids to produce the corresponding carboxylic acid esters, e.g. catalysts such as sulfuric acid, ethylsulfuric acid and diethylsulfate. Japanese Unexamined Patent Publication (Tokkyo Kokai) No. 46587/1975 discloses aromatic disulfonic acid catalysts such as benzenedisulfonic acid. These aromatic disulfonic acid catalysts are advantageous of high activity and low corrosiveness to apparatuses in comparison with the other known catalysts. However, these catalysts exhibit high activity only in a short period of reaction time. That is to say, though the catalyst activity is high in the initial stage of the reaction and carboxylic acid esters can be produced in a high space time yield, the activity is gradually lowered with the progress of the reaction. Thus, the aromatic disulfonic acid catalysts must be improved for the industrial preparation of carboxylic acid esters.
It is an object of the present invention to provide a process for preparing a carboxylic acid ester by the reaction of a carboxylic acid and an olefin in vapor phase.
A further object of the invention is to provide a process for preparing an acetic acid ester by the reaction of acetic acid and an olefin in vapor phase in the presence of a catalyst.
A still further object of the invention is to provide a process for preparing an acetic acid ester in high yields over a long period of time.
These and other objects of the invention will become apparent from the description hereinafter.